Means for starting internal combustion engines of the opposed piston type



Jan. 6, 1959 PETERSEN 2,867,374

MEANS FOR STARTING INTERNAL COMBUSTION ENGINES OF THE OPPOSED PISTONTYPE Filed July 16, 1954 2 Sheets-Sheet 1 Fig.3

AWE/viola HA Ms PETER-551V A'r-roRN Y Jan. 6, 1959 H. PETERSEN 2,857,374

MEANS FOR STARTING INTERNAL COMBUSTION ENGINES OF THE OPPOSED PISTONTYPE Filed July 16, 1954 2 Sheets-Sheet 2 Fig.4

Fig. 3a

1% N5 757525 EN 5, idl 5 @6 2? United States Patent MEANS FOR STARTINGINTERNAL COMBUSTION ENGINES OF THE OPPOSED PISTON TYPE Hans Petersen,Surth (Rhine), Germany Application July 16, 1954, Serial No. 443,948

Claims priority, application Germany June 27, 1953 7 Claims. (Cl.230-56) This invention relates to means for starting internal combustionengines having opposed pistons. More particularly, the invention relatesto the starting of such engines by means of a compressed gas suflicientfor one starting stroke in respect to pressure and quantity.

Conventionally, engines of the opposed piston type are started bymanually opening a valve of a container in which the compressed gas,under a predetermined pressure and in a predetermined volume found to bethat required for a single starting stroke, is stored. The pistons, whenin their starting position, are directly impinged upon by the compressedgas.

An undesirable feature of this arrangement resides in the fact that itis practically impossible'to operate the starting valve by hand withsufiicient speed to expose im-' mediately the entire cross-section of.the passage, so that the opposed pistons may be impinged upon with 'a'shock like force, under full pressure... In consequence, the pistons,asjsoon as they overcome the staticfriction start to move when the valveis only partly open-,., that is, before the entire cross-section of-'.the passage of. the starting valve has been .exposed' and the-pressure.has been fully built up back of the piston. Hence, the full force of thecompressed gas necessary for moving the piston through its first workingstroke, is not available in time. Under these circumstances, the enginedoes not start.

Devices are also known whereby the starting valve will be opened by asuitable mechanical or pneumatic means with a shock-like force, so thatthe opposed pistons will be impinged upon immediately by the fullconcentration of compressed gas. However, great ditficulties areencountered in designing such starting valves so that they operatesafely, since very great forces occur during the action, which forcesmust be taken up in some way.

Another starting means has also been proposed in which one or more ofthe pistons of the cylinders are impinged upon by compressed gas.\First, a space outside the cylinder is filled with the starting gas. Atthis time, the pistons are in a starting position and prevent admissionof the gas to the cylinders. When the desired starting pressure has beenreached, the pistons are moved by a special device a distance such thatthey admit the starting air or other gas from the charged space to thecylinders.

Thus, the starting requires two separate operations which take place oneafter the other. In the first operation, the starting space outside thecylinder, in which the energy necessary for one starting stroke isstored, is charged with a gas under suitable pressure by opening a valvenormally closing a starting container. Simultaneously, via the startingspace or spaces, the areas behind the pressure valves of the cylinderare charged to working pressure. This is done in order to insure themaintenance of pressure necessary for keeping the engine running. Afterthis step has been completed, the second step takes place. A smallamount of starting air is caused to enter in the rear of the pistons bymeans of a 2,867,374 Fatented Jan. 6, 1959 'ice special device in orderto initiate the starting movement of the pistons, and to move them adistance suflicient for them to admit the starting air from the filledstarting spaces to the cylinders.

This method of starting is deficient due to the fact that the pistons,in the starting position, do not completely prevent admission of thestarting air to the cylinders. During the first step, small quantitiesof starting air enter the area at the rear of the pistons from thespaces outside the cylinders while said spaces are being charged,leakages between piston and cylinder being um avoidable. As a result,the pistons start to move after having overcome the static frictionbefore the spaces outside the cylinders are charged to full operatingpressure.

The present invention has as an important object the elimination of theabove described deficiencies.

According to the invention an essential feature of the starting means isa two-phase impingement of the compressed gas upon the opposed pistons.The arrangement is characterized by the fact that the phases areinitiated at different times, with the one phase changing into theother. In the first phase, i. e. the initiating of the starting stroke,the movement of the opposed pistons is started by a throttledimpingement of the compressed gas on the pistons, caused by throttlebores or other throttling means, which e. g. may be a piston ring slot.In the second phase, i. e. the starting stroke proper, theopposedpistons are impinged upon by the gas under full pressure, throughlateral slots arranged in the cylinder walls of the starting strokespaces.

The two-phase operation is initiated by the opening of a starting valveactuatedmanually, mechanically, pneumatically or hydraulically, wherebythe compressed gasesare adrnitted into the starting conduits from astart-ing container which will have been pro-charged with gas under aselected pressure and in a predetermined quantity.

In order to prevent the pistons from beginning their movement before thestarting valve is fully opened and the entire cross-sectional area ofthe passage is exposed, and in order to have fully available thepressure and quantity of the compressed starting gas needed for thestarting stroke, the entrance of the gas into the piston cylinders isslowed under rigidly controlled conditions.

This is accomplished by virtue of the fact that in the starting positionof the pistons, the main entry ports of the cylinders are covered by theopposed pistons, whereas the starting gas supply conduits are kept infull and constant communication with the interiors of the cylinders bythe throttle bores or other throttling means. As a result, thecompressed gas first enters the cylinder through the throttle bores, insmall quantities only. At this stage, the main entry ports are sealed,in the initial or starting position of the pistons, against pressurelosses, by disposition of the piston rings of the opposed pistons onboth sides of said ports in the longitudinal direction of the cylinder.

The throttle bores or other throttling means are so dimensioned as tocross-sectional area that, in the first phase of the starting operation,the building up of the pressure in the cylinders in the rear of theopposed pistons, and the movement of the pistons up to the full openingof the main ports, will not be completed before the manually operablestarting valve, which closes the starting container is fully opened, andthe pressure at the starting slots or main ports is equal to thepressure in said container.

The throttling bores or other throttling means may be formed ininterchangeable inserts screwed into or otherwise removably attached tothe cylinder or pistons, whereby the size of the throttle bore or otherthrottling means may be adjusted as desired.

The entrance of the compressed gas into the cylinder during the secondphase of the starting operation will be controlled by the opposedpistons proper, in that the latter pass over andthus uncover thestarting slots or ports. at a predetermined time. At this time thecross-sectionalareas of the inlets into the cylinder become so largethat full pressure is present in the cylinder when the starting slotsare fully uncovered. Consequently, equalization of pressure occursthroughout the entire compressed gas starting system before the gasbegins to expand.

In the second phase adiabatic expansion of the gas to atmospheric orscavenger air pressure takes place, the cross-sectional areas of thepassages defined by the starting slots being so dimensioned that nothrottling occurs, while in each position of the opposed pistons equalpressure prevails in all spaces in which the expansion takes place. Inorder to permit the gas to leave the cylinder, slots are provided in thecylinder Walls at the end of the expansion stroke, which slots connectthe starting stroke space of the cylinder with atmosphere or with areceiver for scavenger air. In the latter case, the compessed gas passesunder pressure from the starting cylinder into the receiver, and chargesthe receiver partly or entirely up to operating pressure.

In order to fill the scavenger air receiver with fresh air, thereby toclear the internal combustion cylinder of exhaust residues prior to thestarting of the engines, it is advisable to provide the opposed pistonswith throttle bores in such a manner that in the starting position, thethrottle bores connect the scavenger air receiver with the startingconduits. The compressed air for starting the engine can be taken in amanner known per se from a compressed air bottle, which may be chargedby a compressor driven by the opposed piston machine.

The compressed gas bottle, the contents of which sufiice for repeated orsuccessive starting of the machine, may also be charged by compressedgas from the internal combustion cylinder, in which event the compressedgas is taken from the cylinder below the inner dead center position ofthe internal combustion piston. Thus, the compressed gas is taken insmall quantities on each stroke, before the compression end pressure hasbeen reached, and partly after completed combustion, during theexpansion of the gas.

The starting, according to the process hereinbefore described, can beaccomplished on the side of the motor as Well as on the side of thecompressor, and the motor cylinder scavenger pump, one or morecompressor stages, and/or special butters may be used as starting strokespaces.

In the starting of opposed piston engines on the motor side, the energyof motion of the opposed pistons, caused by the starting compressed gas,will first be stored in the compressor stages or in separate butters.After the reversal of the direction of movement, these energies causethe return movement of the opposed pistons and the compression of thecharge of the motor cylinders to ignition temperature.

If the compressor cylinders are used as starting'stroke spaces, they canbe in continuous communication with a starting space or spaces locatedexteriorly of the compressor cylinders, by means of starting slotsarranged in the cylinder walls, without requiring the mounting of aspecial starting valve therebetween. The starting pres sure gas will bedirected in selected pressure and quantity into the mentioned startingspace or spaces. In the starting position, the compressor pistons coverthe starting slots and prevent larger quantities of compressed gas fromentering the starting stroke spaces. Communication of the startingstroke spaces with the atmosphere by means of venting valves preventspressure from building up in the rear of the compressor pistons, whichmay otherwise occur owing to the entrance of small quantities ofcompressed gas from the starting spaces located outside the compressorcylinder, into the starting stroke spaces proper within the cylinder.Thus, the compressor pistons are prevented from starting to moveprematurely.

While the venting valves-are open, the starting spaces outside of thecompressor cylinder and also the spaces in the rear of the pressurevalves of the compressor stages will first be filled with starting airwhile the compressor pistons remain in the starting position, thestarting slots being covered.

Only after this step will the starting process proper be initiated, byclosing of the venting valves arranged in the starting stroke spaces. Inconsequence, pressure will now build up in the rear of the compressorpistons, whereby the beginning of the movement of the opposed pistonswill be initiated and the starting operation according to the two phaseprocess will be accomplished.

In the drawing forming a part of this application, like referencenumerals designate like parts throughout. In said drawing:

Fig. 1 is a section of a part of a starting cylinder equipped for thestarting process, the illustrated position of the piston showing theinner dead center position and further constituting the startingposition,

Fig. 2 is a diagrammatic view showing the theory of the startingoperation,

Fig. 3 is a largely diagrammatic illustration showing the application ofthe invention to a single stage internal combustion engine-aircompressor,

Fig. 3a is a fragmentary, diagrammatic illustration, on an enlargedscale, of certain details of the compressor cylinder structure shown inFig. 3, and

Fig. 4'is a view similar to Fig. 3 showing the starting arrangement fora two-stage internal combustion engineair. compressor.

7 In Fig. 1, a reciprocating piston 91 is provided in a startingcylinder 92, in a starting position. Starting slots or'main gas entryports 93 are covered by piston 91 in the starting position. Piston rings94 and 95 extend about the'piston 91, at both sides of the slots 93. Athrottle bore 97 is provided in the starting cylinder 92 for theentrance of the compressed gas into a starting clearance space 96.Discharge slots 98 are provided for the discharge of the expandedstarting air at the end of the expansion stroke.

Fig. 2, which is a pressure-volume diagram, shows the change of pressureduring the passage of time in the starting process, by the diagram areaABCDEFGI-I. In the position A piston 91 is in the starting position.During the first phase of the starting process, compressed air entersthe starting or clearance space 96 through the throttle bore 97 in thestarting cylinder 92. The throttled impingement of the compressed gas onthe piston 91 is represented by the distance AB in the diagram.

If the pressure is reached at point B the static friction of piston 91in the starting'cylinder 92 will be overcome and the piston will startto move. The stroke initiating the starting, characterized by thedistance BC in the diagram, is finished at the point C and thus thefirst phase of the starting process is completed. On reaching point Cpiston 91 passes the starting slot 93 in the starting cylinder 92 and arapid pressure rise occurs which is illustrated in approximation by thedistance CD in the diagram. A sudden acceleration is imparted to thepiston 91 While the compressed gas expands adiabatically in cylinder 92.This occurrence is illustrated by the distance D-E. When thepiston 91reaches the point E it passes over the discharge slot 98 in cylinder 92and the compressedair leaves the latter under a sudden pressure dropillustrated by the distance BF. Over the distance F-G the startingstroke space is in communication with atmosphere or with a scavenger airreceiver. At point G piston 91 has reached its end position, at whichthe second phase of the starting operation is completed. The returnstroke of the piston 91 is then caused by the combustion occurringin'the cylinder of the internal combustion engine.

Fig. 3 shows, by way of example, a single stage internal combustionengine-air compressor of conventional design. The pistons 1 and 2, and 3and 4, are arranged in the cylinders 5 and 6, respectively, so as tooperate in opposite directions. The pistons 1, 2, 3 and 4 have enlargedportions 101, 102, 103 and 104, respectively,

which move in correspondingly shaped continuations of the cylinders 5and 6, respectively. The pistons 1 and 3 are movably connected byconnecting rods 7 with rocking lever 8, and the pistons 2 and 4 areconnected by connecting rods 7 with the reciprocating lever 9.

The levers 8 and 9 are pivoted upon pins 10, 11, respectively, inhousing 12. It will further be noted that the levers are connected toone another by means of a synchronizing rod 13. Rod 13 is pivotallyconnected at its opposite ends to the levers, eccentrically with respectto the pivot points of the levers.

As a result, synchronized movement of the pairs of pistons is insured. Acommon stroke chamber 14 is defined between the oppositely movablepistons 1 and 2.

is provided with inlet slots 15, outlet slots 16, and injection nozzles17. Of larger diameter than the chamber 14 are the cylinder spaces 18,19, said spaces having a diameter equal to the diameter of the enlargedportions 101, 102 of the pistons. Spaces 18, 19 are designed asscavenger and charging pumps, and are provided with suction valves 20,21, respectively, and pressure valves 22, 23, respectively.

The interior of the housing serves as a scavenger air receiver 24, andis sealed against communication with the atmosphere by housing covers25, 26.

A common stroke space 27 is defined between the oppositely movablepistons 3 and 4. This constitutes a first compressor stage, and isequipped with a suction valve 28 and a pressure valve 29. Spaces 30, 31analogous .to spaces 18, 19, serve as buffer spaces, and also con-.stitute starting stroke spaces.

' During the starting operation, stroke spaces 30, 31 are respectivelyconnected to the outlet ends of the branches of a starting conduit 36,by means of inlet slots or main gas entry ports 32, 33, respectively,throttling bores 132 and 133, respectively, and automatic startingvalves 34, 35. In addition, the stroke spaces 30 and 31 are connectedwith the scavenger air receiver 24, so as to communicate therewith, bymeans of discharge slots 37, '38, the communication of spaces 30 and 31with the receiver occurring at the outer dead center position of thepistons 3 and 4, respectively.

Also included in the construction is a compressed gas bottle 39 havingvalves 40, 41, a reduction valve 42, a starting container or reservoir43, and a hand-actuated starting valve 44 provided with a hand lever 45.The .compressed gas bottle 39 is connected in communication with thestarting container 43 by a line 46, and the starting'container 43 andthe starting valve 44 communicate with one another through the medium ofa pipe line 47.

Extending from stroke space 14 to the bottle 39 is a line 49, throughwhich pressure gases travel from the stroke space 14 during thecompression and expansion strokes of pistons 1 and 2, said gases beingthus transferred from the space 14 to the bottle. A valve 48 is providedin line 49.

In order to move the pistons 1, 2, 3 and 4 into their startingpositions, a lever 50 is provided, which is removably attached to anon-circular extension 51 of the pin of lever 8.

in comparing Fig. l with Fig. 3, it will be noticed that the elements91, 92, 93, 96, 97 and 98 of Fig. 1 correspond to the parts 104, 12, 33,31, 133, and 38, respectively. The arrangement on the side of piston 3with respect to the starting slots 32 and 132, the space 30 and thedischarge slot 37 is a mirror image of the arrangement of thecorresponding elements on the side of piston at their confronting ends.

corresponding First, lever 50 is manually swung to shift pistons 1,

2, 3 and 4 into their starting positions. For this purpose, the strokespaces 30 and 31 may be vented in any suitable manner not specificallyillustrated.

The starting positions will have been reached when pistons 3 and 4 incylinder 6 abut against one another In this position of the parts, lever50 is removed. Now, the valve 41 is opened and container 43 will becharged to starting pressure through reduction valve 42 and line 46.Fuel is injected by a suitable fuel pump, not shown, through injectionnozzle 17 into the stroke space 14 of the internal combustion cylinder5.

Starting valve 44 is now opened by means of lever 45. As a result, gasflows from container 43 through valve 44, line 36, and valves 34, 35, tothe throttle bores 132 and 133, and the inlet slots 32 and 33. Both thethrottle bores and the inlet slots are in communication with the outletends of the branches of line 36.

Thereafter, the two phase starting operation will take place in themanner described hereinbefore with respect to Figs. 1 and 2. As aresult, pistons 3 and 4 will initially be moved to uncover inlet slots32 and 33. As soon as the slots are uncovered, gas flowing therethroughwill impinge upon the pistons 3 and 4, and the pistons will thereupon beurged apart with high acceleration, simultaneously with movement ofpistons ,1 and 2 toward one another.

The air contained in the stroke space 14 will now be compressed toignition temperature. Immediately before pistons 1 and 2 reach theirinner dead center positions, fuel will be injected through nozzle 17into space 14. Combustion thus occurs in space 14, causing pistons and 2to be again forced apart. Air will, as a result, be sucked fromatmosphere through suction valves 20 and 21 into stroke spaces 18, 19.

While the pistons 1 and 2 are urged apart, pistons 3 and 4 move intotheir inner dead center position once again. Accordingly, the aircontained in spaces 30 and 31 will be compressed, causing valves 34, 35to close. Passage of the compressed air into the line 36 will, as aresult, be prevented. The air compressed in stroke spaces 30. and 31will cause the return movement of the pistons 3 and 4, and 1 and 2. I

During the movement of pistons 3, 4 toward one another, the aircontained in the stroke space 27 is compressed, and isv forced outwardlythrough pressure valve 29, into pressure conduit 52, which leads to acompressed air receiver, not shown.

With pistons 3, 4 in their inner dead center positions, pistons 1 and 2are in their outer dead center positions, and inlet slots 15 anddischarge slots 16 are open, for the scavenging of internal combustionchamber 14. On reversal of the direction of movement, the compressed aircontained in spaces 31), 31 will expand and will transmit its energy topistons 3 and 4. Air 'is, accordingly, sucked into stroke space 27 ofcylinder 6 by means of inlet valve 23, during the outward movement ofthe pistons 3, 4.

On movement of pistons 1 and 2 toward one another, the air drawn intothe stroke spaces 18, 19, will be compressed and will be discharged intothe scavenger air receiver 24, through the pressure valves 22, 23. Incylinder 5, however, the air will be compressed in stroke space 14 toignition temperature. The subsequent working stroke accordingly repeatsitself, in the manner hereinbefore described.

After the engine has been started, the valve 44, as well as valve 41 ofthe bottle 39 will be again closed. Subsequently, during operation ofthe engine, bottle 39 is recharged through valve 48 and conduit 49, fromthe stroke space 14, in the manner previously described. When bottle 39is again fully charged, valve 40 will be closed and sufficient energyfor another starting of the engine is thus stored.

In Fig. 4 the starting means constituting the present invention isillustrated in an application to a two stage compressor having opposedpistons of conventional design.

In this arrangement, space 14, having inlet slots 15 and discharge slots16, and charged with fuel through nozzle 17, is provided in the samemanner, in an internal combustion engine, as previously described withreference to Fig. 3. Further, as in Fig. 3, stroke spaces 18 and 19,having suction valves 20 and 21 and pressure valves 22 and 23, aredesigned as scavenger pumps.

In the Fig. 4 embodiment of the invention, stroke spaces 30a and 31a areprovided as first compressor stages. These spaces further serve asstarting stroke spaces. As in the previous form described, slots 32, 33are normally covered by pistons 3 and 4.

At the end of the expansion stroke of the pistons, spaces 30a, 31acommunicate with slots 37 and 38, which slots connect the stroke spaces30a, 31a, in the outer dead center piston positions, with the scavengerair receiver 24. Further, stroke spaces 30a, 31a are connected incommunication with each other, through a compensating conduit 52 andbores 53, 54. In conduit 52 a venting valve 55 is provided, whichcomprises the starting valve means in this embodiment of the presentinvention and can be opened and closed by actuating starting lever 56.When venting valve 55 is opened, conduit 57 connects the compensatingconduit 52, and thus the stroke spaces 30a, 31a, in communication withthe atmosphere.

Exteriorly of compressor cylinders 58, 59, there are provided annularspaces 60, 61 which store the compressed air or gas needed to start theengine, and in which is stored the return movement energy of the pistonpairs 1, 3 and 2, 4, i. e., the energy needed in order to force pistons3 and 4 apart and the pistons 1, 2 toward each other.

In addition, suction valves 62, 63, and pressure valves 64, 65, areprovided in spaces 60 and 61. Said spaces or chambers are furtherconnected in communication with an intermediate cooler 68, throughconduits 66, 67.

The cooler is in communication with stroke space 73 of the secondcompressor stage, through conduits 69, 70 and slots 71, 72. Space 73 isprovided with a suction valve 74, and with a pressure valve 75. Further,space 73 is in communication, on its suction side, with the atmosphere,through the medium of conduit 76. On the pressure side of space 73, onthe other hand, the pressuremaintaining valve 77 is mounted, back ofvalve 75. Space 78, in which compression thus occurs, is of smalldimensions, being so proportioned in terms of its area as to cause fulloperating pressure to be maintained therein on each working stroke ofpistons 3 and 4. Due to this arrangement, the maintenance of pressurenecessary to.

keep the engine in operation is insured in space 73. A conduit 7 9 leadsto a compressed air container, not shown. Spaces 60, 61 are furtherconnected with a reduction valve 82 through the medium of conduits 80,81. Valve 82, in turn, is connected in communication with a compressedgas bottle 84 through the medium of a pipe 83. Compressed air is takenfrom this bottle by means of a stop valve 85.

As in the form of the invention shown in Fig. 3, the compressed gasbottle 84 is charged with combustion gases or compressed combustion airfrom stroke space 14 through valve 48, conduit 49, and stop or controlvalve 40.

In the Figure 4 embodiment, the starting operation occurs in thefollowing manner:

First, lever 50 is manipulated to shift pistons 1, 2, 3 and 4 into theirstarting positions. In these positions, slots 32 and 33 are covered bypistons 3 and 4. Venting valve 55 is now opened by operation of lever56.

Stop valve 85 of bottle 84 is now opened to permit compressed gases topass through conduit 83, reduction valve 82, and conduits 80, 81 intothe chambers 60, 61. The gas passes from said chambers into theintermediate cooler 68 by way of the pressure valves 64, 65 and conduits66, 67. The gas then reaches slots 71 and 72 of cylinder 6 through pipelines 69, 70. In this way, as a first step, the chambers 60, 61 and 68,and the conduits 66, 67, 69 and 70, disposed exteriorly of compressorcylinders 58 and 59, are charged to an operating pressure while pistons1, 3 and 2, 4 remain in the starting position. During this stage of theoperation, small quantities of compressed gas enter stroke spaces 30aand 31a through slots 32 and 33 and also through slots 71 and 72, owingto a necessary piston clearance or piston ring gaps. These quantitiespass to the atmosphere through bores 53 and 54, compensating conduit 52,the open venting valve 55, and conduit 57. In this manner, pressure isprevented from building up in the rear of pistons 3 and 4 in strokespaces 30a and 31a. Thus a premature initiation of the starting movementof the pistons is avoided during the charging of the designated spacesand conduits with compressed gas.

As a next step, fuel is injected by means of a plurality of strokes of ahand-operated fuel pump, not shown, through injection nozzle 17 intostroke space 14 of the internal combustion engine. Then, venting valve55 is closed by starting lever 56. In this way, the parts are preparedfor the starting operation hereinbefore described, with the two phaseimpingement of the gases upon the pistons being initiated by the slowpressure build-up in stroke spaces 30a, 31a due to leakage past thepistons, subsequent freeing of the slots or apertures 32, 33 enablingthe compressed gas to flow rapidly from the annular spaces or reservoirmeans 60, 61 into the stroke spaces so as to cause rapid completion ofthe starting stroke.

It will be apparent to those skilled in the art, that many alterationsand modifications of the structure hereinbefore described andillustrated are possible without departure from the spirit and essenceof the invention which for that reason shall not be limited but by thescope of the appended claims.

I claim:

1. A starting device for a free motor piston machine, comprisingcompressor cylinder means, a pair of free compressor pistonsreciprocally movable in opposite directions in said compressor cylindermeans and constructed for driving connection to the motor piston meansof said machine, each of said compressor pistons when in its inner deadcenter position defining with a respective end portion of saidcompressor cylinder means a corresponding starting stroke space, each ofsaid respective end portions of said compressor cylinder means beingprovided with at least one starting aperture positioned to be obturatedby the associated compressor piston when the same is in said inner deadcenter position thereof, reservoir means in communication with saidstarting apertures and constructed to contain at a predeterminedoperating pressure a quantity of compresser gas sufficient for only onestarting stroke of said compressor pistons, said compressor cylindermeans defining additionally from said reservoir means to each of saidstarting stroke spaces a flow path of substantially restrictedcross-section relative to said starting apertures, and starting valvemeans communicating with said starting stroke spaces and operable tocontrol the build-up of pressure in said starting stroke spaces, wherebyupon operation of said starting valve means to permit a pressure buildupin said starting stroke spaces, compressed gas flows from said reservoirmeans via said flow path into said starting stroke spaces at arelatively slow rate determined by the restricted crosssection of saidflow path to slowly initiate said pressure build-up and thus saidstarting stroke of said compressor pistons, while upon continuedmovement of the latter during said starting stroke thereof in saidcompressor r 9 cylinder means, said starting apertures are freed andsaid compressed gas then flows from said reservoir means via saidstarting apertures into said starting stroke spaces at a relatively highrate determined by the relatively larger cross-sections of said startingapertures to thereby effect a rapid pressure build-up and subject saidcompressor pistons substantially immediately to the full operatingpressure so as to rapidly complete the starting stroke of saidcompressor pistons.

2. A starting device for a free motor piston machine, comprisingcompressor cylinder means, a pair of free compressor pistonsreciprocally movable in opposite directions in said compressor cylindermeans and constructed for driving connection to the motor piston meansof said machine, each of said compressor pistons when in its inner deadcenter position defining with a respective end portion of saidcompressor cylinder means a corresponding starting stroke space, each ofsaid respective end portions of said compressor cylinder means beingprovided with a first aperture positioned to be obturated by theassociated compressor piston when the same is in said inner dead centerposition, each of said respective end portions of said compressorcylinder means being further provided with a second aperturesubstantially restricted in cross-section relative to the associatedfirst aperture and communicating with the corresponding starting strokespace, a container for compressed gas constructed to contain at apredetermined operating pressure a quantity of compressed gas sufiicientfor only one starting stroke of said compressor pistons, conduit meansestablishing communication between said container and said apertures ineach of said end portions of said compressor cylinder means, startingvalve means arranged in said conduit means and operable when closed toinhibit flow of compressed gas through said conduit means, and checkvalve means arranged in said conduit means for permitting fiow ofcompressed gas only in the direction from said container to saidapertures, whereby upon opening of said starting valve means with saidcompressor pistons in their dead center positions, compressed gas flowsfrom said container through said conduit means past said check valvemeans and via said second apertures into said starting stroke spaces ata low rate determined by the restricted cross-sections of said secondapertures to initiate slowly the starting stroke of said compressorpistons, while upon continued movement of said compressor pistons duringsaid starting stroke thereof said first apertures are freed and gas thenflows via said first apertures into said starting stroke spaces at arelatively high rate determined by the relatively large cross-sectionsof said first apertures for subjecting said compressor pistonssubstantially immediately to the full operating pressure so as tocomplete very rapidly the starting stroke of said compressor pistons.

3. A starting device according to claim 2, said free motor pistonmachine including motor cylinder means, and a pair of motor pistonsreciprocal in said motor cylinder means between inner and outer deadcenter positions, said device further comprising a reserve bottle forcompressed gas, additional conduit means establishing communicationbetween said reserve bottle and said container on the one hand, andbetween said reserve bottle and said motor cylinder means at a point inthe latter below the inner dead center position of said motor pistons onthe other hand, a reducing valve controlling said additional conduitmeans between said reserve bottle and said container, and a tappingvalve controlling said additional conduit means between said reservebottle and said motor cylinder means, whereby said bottle is chargedwith compressed gas taken from said motor cylinder means duringoperation of said machine, which compressed gas may thereafter' beintroduced into said container for a subsequent starting operation.

4. A starting device according to claim 3, further comprising ascavenger air receiver communicating with said motor cylinder means,said compressor cylinder means being provided with respective outletapertures disposed remote from said first and second apertures andpositioned to be traversed by said compressor pistons during saidstarting stroke thereof, whereby upon termination of the movement ofsaid compressor pistons from said inner dead center positions thereofsaid outlet apertures establish communication between said scavenger airreceiver and said compressor cylinder means to permit compressed gasintroduced into said starting stroke spaces to escape into saidscavenger air receiver so as to charge the latter at least partly to itsoperating pressure.

5. A starting device for a free motor piston machine, comprisingcompressor cylinder means, a pair of free compressor pistonsreciprocally movable in opposite directions in said compressor cylindermeans and constructed for driving connection to the motor piston meansof said machine, each of said compressor pistons when in its inner deadcenter position defining with a respective end portion of saidcompressor cylinder means a corresponding starting stroke space, each ofsaid respective end portions of said compressor cylinder means beingprovided with a plurality of starting apertures positioned to beobturated by the associated compressor piston when the same is in itsinner dead center position, each of said starting stroke spaces beingnormally vented to the atmosphere, venting valve means communicatingwith said starting stroke spaces and operable when closed to interruptthe venting of said starting stroke spaces, means surrounding saidrespective end portions of said compressor cylinder means and definingabout said starting apertures a pair of annular spaces adapted tocontain at a predetermined operating pressure a quantity of compressedgas sufficient for only one starting stroke of said compressor pistons,intermediate container means communicating with said annular spaces andsaid compressor cylinder means, check valve means arranged between saidannular spaces and said intermediate container means for permitting flowof compressed gas' only in the direction from said annular spaces tosaid container means, and conduit means in communication with saidannular spaces to supply the same with compressed gas until the latteris at said operating pressure within said container means and saidannular spaces, whereby upon closing of said venting valve means withsaid compressor pistons in their inner dead center positions, compressedgas leaks from said container means and said annular spaces past saidcompressor pistons, due to clearance between the same and saidcompressor cylinder means, into said starting stroke spaces at a lowrate determined bythe restricted dimensions of said clearance to buildup the pressure in said starting stroke spaces and to initiate slowlythe starting stroke of said compressor pistons, while upon continuedmovement of said compressor pistons during said starting stroke thereofsaid starting apertures are freed and said compressed gas then flowsfrom said annular space via said starting apertures into said startingstroke spaces at a relatively high rate determined by the relativelylarger cross-sections of said starting apertures for subjecting saidcompressor pistons substantially immediately to the full operatingpressure so as to complete very rapidly the starting stroke of saidcompressor pistons.

6. A starting device according to claim 5, said free motor pistonmachine including motor cylinder means and a pair of motor pistonsreciprocal in said motor cylinder means between inner and outer deadcenter positions, said device further comprising a reserve bottle forcompressed gas,'said conduit means being connected to said reservebottle, a reducing valve controlling said conduit means between saidbottle and said annular spaces, additional conduit means establishingcommunication between said reserve bottle and said motor cylinder meansat a point in the latter below the inner dead center position of saidmotor pistons, and a tapping valve controlling said additional conduitmeans, whereby said bottle is charged with compressed gas taken fromsaid motor cylinder means during operation of said machine, whichcompressed gas may thereafter be introduced into said annular spaces fora subsequent starting operation.

7. A starting device according to claim 6, further comprising ascavenger air receiver communicating with said motor cylinder means,said compressor cylinder means being provided with respective outletapertures disposed remote from said starting apertures and positioned tobe traversed by said compressor pistons during said starting strokethereof, whereby upon termination of the movement of said compressorpistons from said inner dead center positions thereof said outletapertures establish communication between said scavenger air receiverand said compressor cylinder means to permit compressed gas introducedinto said starting stroke spaces to escape into said scavenger airreceiver so as to charge the latter at least partly to its operatingpressure.

References Cited in the file of this patent UNITED STATES PATENTS351,657 Schofield Oct. 26, 1886 2,101,159 Stevens Dec. 7, 1937 2,222,260Janicke Nov. 19, 1940 2,306,978 Pateras Pescara Dec. 29, 1942 2,334,688Norton Nov. 16, 1943 2,408,031 Beale Sept. 24, 1946 2,423,720 Mullejanset a1. July 8, 1947 2,585,940 Juilfs Feb. 12, 1952 FOREIGN PATENTS541,779 Great Britain Dec. 11, 1941

